Solids thickened lubricating greases containing formamide



United States Patent 9 SOLIDS THICKENED LUBRICATIN G GREASES CONTAININGFORMAMIDE Norman R. Odell, Fishkill, and Joseph F. Lyons, Poughkeepsie,N.Y., assignors to Texaco Inc, a corporation of Delaware No Drawing.Filed Feb. 6, 1958, Ser. No. 713,540

12 Claims. (Cl. 252-28) This invention relates to improved lubricatinggreases thickened with finely divided solids, and more particularly tosuch greases containing small amounts of formamide, and to methods ofpreparing such greases.

We have found, in the preparation of solids thickened greases, that asmall amount of formamide present in the grease mixture during thehomogenization process assists in the development of the gel structureand very materially improves the yield and stability of the product.This efiect obtained by the use of formamide is unexpectedly very muchgreater than that obtained with various other liquids such as water,which are commonly employed in solids thickened greases in small amountsto assist in the gel formation.

The solids thickened greases which are benefited by the presence ofsmall amounts of formamide in accordance with this invention are thosewherein the solid thickening agent is a finely divided polar material,such as, for example, silica and certain naturally occurring siliceousmaterials such as bentonite, organo-clays obtained by treating bentonitewith amines of various types, organic pigments of various types such asphthalocyanines, indigo, etc., having a measurable surface polarity, andmetal oxides of various types such as zinc oxide, magnesium oxide,aluminum oxide, etc., having the property of thickening lubricating oilswhen they are dispersed therein in finely divided form in suitableproportions. Such materials are suitably employed in the form ofparticles below about microns in diameter, and usually having a diameterbelow about two microns in diameter, although the most suitable particlesize and form will vary somewhat with the type of material employed.

In general, it is found that the effectiveness of formamide as a yieldimproving agent increases with increasing polarity of the solidthickening agent. However, special advantages are obtained in certaincases with thickening agents of only relatively low polarity. Forexample, in the preparation of organo-clay thickened greases employingthe so-called in situ process, wherein the organo-clay is formed bytreating bentonite with an amine or an amine salt in the presence oflubricating oil comprising all or a portion of the oleaginous liquidcomponent of the grease, it has been found that an unexpected yieldadvantage is obtained when the formamide is present during theorgano-clay reaction. Accordingly, the preparation of such greaseswherein an organo-clay is formed in situ in the presence of theformarnide, is regarded as comprising a preferred embodiment of thisinvention.

The greases of this invention comprise an oleaginous liquid as the chiefcomponent, containing about 0.05 to about 5.0 percent of formamide,based on the weight of the grease, and a finely divided solid of thecharacter described above in a sufficient amount to thicken thelubricating oil to a grease consistency with the aid of the formamidewhich is present. Ordinarily the amount of solid thickening agent ispresent in amounts from about 5 to about 45 percent by weight, based onthe weight of the grease, and preferably in amounts from about 7 toabout 2.5 percent by weight, according to the thickening action of thesolid and the grease consistency desired. The formamide is preferablyemployed in an amount between about 0.1 and 3.0 percent of the weight ofthe grease composition.

The lubricating oils employed in these greases may be any suitable oilsof lubricating characteristics ordinarily employed in lubricatinggreases, including the conventional mineral lubricating oils, syntheticoils obtained by various refinery processes, such as cracking andpolymerization, and other synthetic oleaginous compounds, such as highmolecular weight ethers, esters, silicones, etc. Suitable mineral oilsinclude paraflinic and naphthenic oils having viscosities in the rangefrom about seconds Saybolt Universal at F. to about 225 seconds SayboltUniversal at 210 F., and are preferably those having viscosities in therange from about 100 to about 600 seconds Saybolt Universal at 100 F.

Additives of the usual types employed in solids thickened greases,including oxidation inhibitors, rust and corrosion inhibitors, extremepressure agents, etc., may be employed in these greases where noantagonistic effect results between such additive and the formamide.Such materials are employed in minor amounts, such as from about 0.05 toabout 10.0 percent by Weight, and preferably in amounts from about 0.5to about 5.0 percent by weight of the grease. A very suitable class ofoxidation inhibitors are the aromatic amines, such as for example,diphenylamine, alphaand beta-naphthylamines and para-phenylenediamine.Very advantageously a compound of the class of higher aliphatic aminesand amides, wherein an aliphatic hydrocarbon group contains about 1025carbon atoms, is employed in the composition in order to improve thewater resistance and other properties. We have found that formamideoffsets or overcomes the yield depressing effect commonly resulting fromthe use of compounds of this type in solids thickened greases to asufiioient extent that solids thickened greases having good Waterresistant properties are obtained in satisfactory yields by employingboth higher aliphatic amines or amides and a small amount of formamidein the composition.

As an example of a preferred embodiment of this invention, greases wereprepared containing a surface treated bentonite as the thickening agentand containing a small amount of formamide, which was present during thebentonite-amine reaction. The preparation of the solid thickening agentwas carried out by treating a micron sized bentonite with a commercialquaternary amine salt mixture, comprising about 75 percent by weight ofdioctadecyland dihexadecyl-dimethyl ammonium chlorides in a weight ratioof 70:30, respectively, in isopropyl alcohol. The reaction was carriedout in the presence of the mineral lubricating oil employed in thegrease, employing stoichiometric amounts of the amine salts andbentonite on the basis of the measured base exchange capacity of thebentonite. A typical grease preparation was carried out in the followingmanner: 113 grams of the commercial amine salt mixture was mixed with2,112. grams of a refined paraffinic residual oil having a gravity, APIof 26.0, a Saybolt Universal viscosity at 100 F. of 977 seconds and aviscosity index of about 80, the mixture heated to 250 F. and circulatedin a Manton-Gaulin homogenizer at 5000 pounds pressure di.f

3 4 ferential while 200 grams of bentonite and then 4.8 grams Table IIIof formamide were added. The circulation was continued for 45 minutes.The following table shows the yield and penetration at stability of theproduct thus obtained as compared with a grease prepared in theidentical way except that 4.8 5 Additives Worked on Worked grams ofwater was added instead of the formamide. Unwmked Strokes Table I NoneLtquid Composition, Wt. Percent, Calculated: 06% Formamlde 332 n 341 379Organo clay 11.5 11.5 10 Sac;gratinchlori e 8g 3-3 1 Converted from sizecone, }4 size worker used. g r n agiga As shown by the data given in thetables, very ma eri- Penetration, ASTMat 5p; ally improved yields areobtained by employing Sma l %i rgg l rei $3 533 amounts of formamide ingreases thickened with polar penetration solids of various types,including such greases containing r -10,000 stro s 311 higher aliphaticamines and amide having a yield depress- As shown by the above table, astable grease was obtained in satisfactory yield by employing 0.2 weightpercent of formarnide in conjunction with the organo treated bentoniteas the thickening agent. On the other hand, the same amount of water wasineffective to produce a stable grease structure in this composition. Bythe use of larger amounts of water, up to about 1 percent, substantialyield improvements were obtained in greases of this type, but these werestill considerably lower than those obtained with equivalent or loweramounts of formarnide.

Table II below shows the efiect of formamide in improving the yield in adifferent solids thickened grease, and also shows its effect inoffsetting the yield depressing effect of higher aliphatic amines andamides which were employed to improve the water resistant properties ofthe grease. The greases comprised 15.0 percent by weight of finelydivided silica, having an average particle size of 0.022 micron and asurface area of 160-175 square meters per gram, in a refined naphthenebase oil having a Say bolt Universal viscosity at 100 F. of about 310seconds. The preparation was carried out by mixing together the solidthickener and additives with the lubricating oil at room temperature andfinishing by milling in a Premier colloid mill with two passes at 0.002inch clearance.

Table II Grease Composition, Percent:

Silica 15.0 15.0 15.0 Formamide l) 1.5 0.3 N,N-di- (beta by 0 0 1.0

droxyethyl) 12-hydroxysteararnide. Duomeen T 1 0 0 2.0--.. 2.0 0 0Lubricating Oil 85.0 83.5 83.0... 81.5 84.0.-. 83.2 AS'EM Penetration atUnworked 331 317 400+-- 356 347-.-- 297 Worked60 strokes... 380 331 400390 400+" 341 Worked100,000 400+ 315 381 345 strokes. Dynamic WaterResist- 100 100 Too 4 Toe ance Test, percent loss. soft soft for fortest. test.

1 Commercial mixture of compounds having the formula RNHGflI NHi, whereR is an alkyl group derived from tallow.

As shown by the above table, the use of a small amount of form-amidevery materially increased the yield and stability of the silicathickened grease, and also offset the yield depressing effect of ahigher aliphatic amine and amide, so that by the use of these additiveswith formamidc, silica thickened greases having good water resistanceproperties were obtained in satisfactory yields.

The following table shows the effect of formamide in a solids thickenedgrease of a still diiierent type. This was a grease comprising as thethickening agent percent by weight of finely divided zinc oxide, havingan average particle size of 0.12 micron, in a refined naphthenicdistillate oil having a viscosity at 100 F. of about 310 seconds. Thepreparation was carried out in the manner described for the silicathickened grease above.

ing effect. In addition, the greases containing formamide have greatlyimproved working stability, as shown by the smaller amount of changewhich occurred in the greases of the examples upon working 10,000 or100,000 strokes in the ASTM worker test.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. A lubricating grease consisting essentially of a major amount oflubricating oil, about 5-45 percent by weight of a finely divided polarsolid having the property of forming gels with lubricating oils,selected from the class consisting of bentonites which have been surfacetreated with higher aliphatic amines, silica and oxides of zinc,magnesium and aluminum, and about 0.505.0 percent by weight offormamide, said finely divided polar solid being present in an amountsufficient to thicken the composition to a grease consistency.

2. A lubricating grease according to claim 1 wherein the formamide ispresent in an amount of 0.1-3.0 percent by weight.

3. A lubricating grease according to claim 1 wherein the said finelydivided polar solid is bentonite which has been treated with a compoundchosen from the class consisting of higher aliphatic amines and saltsthereof.

4. A lubricating grease according to claim 1 wherein the said finelydivided polar solid is silica.

5. A lubricating grease according to claim 1 wherein the said polarsolid is zinc oxide.

6. A lubricating grease according to claim 1 wherein the said greasecontains about 0.05- percent by weight, suificient to improve its waterresistant properties, of a compound selected from the class consistingof higher aliphatic amines and amides.

7. A lubricating grease according to claim 6 wherein the said amides arealkanolamides of higher fatty acids.

8. A lubricating grease consisting essentially of a major amount ofmineral lubricating oil, about 7-25 percent by weight, suflicient tothicken the composition to a grease consistency, of finely dividedsilica, about 0.1-3.0 percent by weight of formamide and about 05-50percent by weight of a compound chosen from the group consisting ofhigher aliphatic amines and amides.

9. A lubricating grease according to claim 8 containing 0.5-5.0 percentby weight of N,N-di-(betahydroxyethyl)- IZ-hydroxystearamide.

10. A lubricating grease according to claim 8 containing 0.5-5.0 percentby weight of a compound having the formula RNHC H NH where R is analiphatic hydrocarbon group containing lO-25 carbon atoms.

11. The method of grease preparation which comprises providing a mixtureconsisting essentially of a lubricating oil, about 545% by weight basedon the weight of the mixture of a finely divided oil insoluble highmelting solid having a measurable surface polarity and having the prop-5 6 erty of forming gels in lubricating oils, and about 0.05 offormamide and shearing the said mixture until a grease 5% by weight offormamide, and subjecting the said mixconsistency is obtained.

cure to shearing until a grease consistency is obtained.

References Cited in the file of this patent 12. The method of greasepreparation which comprises heating together a mixture of lubricatingoil, a minor 5 UNITED STATES PATENTS amount of a compound chosen fromthe class consisting 2,592,863 Her 09L 26, 1954 of higher aliphaticamines and salts thereof, about 5-45% FOREIGN PATENTS by weight ofbentonite and about ODS-5.0% by weight 735,711 Great Britain Aug 24, 55

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,986,517 May 30, 1961 Norman R. Odell et al.

it is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 35, for "O.505.0" read OO55,0

Signed and sealed this 17th day of October 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of PatentsUSCOMM-DC

1. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OFLUBRICATING OIL, ABOUT 5-45 PERCENT BY WEIGHT OF A FINELY DIVIDED POLARSOLID HAVING THE PROPERTY OF FORMING GELS WITH LUBRICATING OILS,SELECTED FROM THE CLASS CONSISTING OF BENTONITES WHICH HAVE BEEN SURFACETREATED WITH HIGHER ALIPHATIC AMINES, SILICA AND OXIDES OF ZINC,MAGNESIUM AND ALUMINUM, AND ABOUT 0.05-5.0 PERCENT BY WEIGHT OFFORMAMIDE, SAID FINELY DIVIDED POLAR SOLID BEING PRESENT IN AN AMOUNTSUFFICIENT TO THICKEN THE COMPOSITION TO A GREASE CONSISTENCY.